Semiautomatic metal casting apparatus

ABSTRACT

A program-controlled semiautomatic metal casting process and apparatus involving a series of successive working and checking operations, including preliminary semiautomatic startup operations and final fully automatic melting, pouring, and shutdown operations. Commencement of each operation requires proper completion of the preceding operation. Certain of the operations proceed in accordance with a preselected casting program which may be varied, either by total program substitution or by manual adjustment of the individual program parameters, to provide the optimum program for the particular metal being poured and the particular shape being cast.

United States Patent [72] Inventors Frank L. Hetzel 3,008,855 11/1961Swenson 164/256 UX Manhattan Beach; 3,478,808 1 1/1969 Adams 164/4Stuart T. Schy, Reseda, both of Calif. 3,525,382 8/1970 Devol 164/1549Y1; 3 1:2 FOREIGN PATENTS 1 e u y [45] Patented Nov. 16 1971 467,4756/1937 Great Bntam 164/157 [73] Assignee TRW Inc. Primary ExaminerR.Spencer Annear One Space Park, Redondo Beach, Calif. A!trneys Daniel T.Anderson, Donald R. Nyhagen and Jerry A. Dinardo 4 EM l 3 s: CASTINGAPPARATUS ABSTRACT: A program-Controlled semiautomatic metal castingprocess and apparatus mvolvmg a series of successive [52] US. Cl164/155, working and checking operations, including preliminary /258semiautomatic startup operations and final fully automatic [51] Int. Cl822d 37/00 m lti g, ouring, and shutdown operations. Commencement [50]Field ol Search 164/4, 61, of ea h o eration requires proper completionof the preceding I55 operation. Certain of the operations proceed inaccordance with a preselected casting program which may be varied. [56]References cued either by total program substitution or by manualadjustment UNITED STATES PATENTS of the individual program parameters,to provide the optimum 2,713,183 7/1955 Winkler 164/258 p g for the p rl me l ing p re nd th par- 2,932,069 4/1960 Takahashi et al 164/256ticular h p eing a t.

VAC POWER CONTROLLER 52 SUPPLY 5o 28 TEMP 3 MOLD MONITOR l POLBHON CONROLLER CARD :2 PROGRAMMER |2 L, VAC

54 PUMPING MEANS 42 PROGRAM 401 SEOUENCER ;1 C

MASTER CONTROL MANUAL CIRCUIT PROGRAMMER L 1s LECEL 34 MOLD on F I I 4456 GU58 CRUCIBLE SSi TROLLER 430 434 45 4,2 432 436 0% o 0 0 HEATCONTROL PANEL CONTROLLER PATENTEDuuv 16 an SHEET 07 0F 250 Frank LHefzel Stuart T Schy 24s INVENTORS Fig 50 ATTORNEY PATENTEDuuv 16 I97!3, 20,294

sum 12 0F 12 SOOb - 7 o 282A-F Frank L; Hetzel Flg- L Stuart T Schy INVENTORS ATTORNEY SEMIAUTOMATIC METAL CASTING APPARATUS BACKGROUND OFTI-IE'INVENTION l. Field of the Invention This invention relatesgenerally to the metal casting art. More particularly, the inventionrelates to a programmed, semiautomatic metal casting method andapparatus involving successive semiautomatic and fully automatic workingand checking operations, certain of which proceed in accordance with acasting program which may be varied to provide the optimum program forthe particular metal and shape being cast.

2. Prior Art As will appear from the ensuing description, the presentinvention may be utilized for both atmospheric and vacuum castingapplications. However, the invention is primarily concerned with andwill be disposed in relation to vacuum casting.

Heretofore, vacuum casting of super alloys and other exotic metals hasgenerally required manual control and manipulation of the castingapparatus. As a consequence, evaluation of the various steps of thecasting process often vary from one operator to the next with the resultthat castings of uniform quality are difiicult to obtain. Moreover,these manually controlled casting processes are excessively tedious andtime consuming to practice owing to the numerous manual working andchecking operations which the operator must perform properly, and in theproper sequence to obtain satisfactory casting. However, even with theutmost care on the part of the operator, errors and improperly performedcasting operations often occur which result in substandard or totallyunacceptable cast parts, as well as other adverse occurrences, such asexcessive splash and hence loss of the metal being poured.

Another disadvantage of the existing manual casting techniques residesin the fact that many of the manual operations performed during thecasting cycle are not subject to audit until completion of the cycle.Consequently, slight variations in the various operations introduced bydifferent operators cannot be detected until the casting cycles arecompleted and then only by detection of variations in the cast parts.This method of detecting and correcting operator-induced variations inthe casting process is very inefiicient, at best, and relatively costlybecause of the nature of the equipment involved, the necessity ofchecking each casting, and the relatively high scrap rate.

SUMMARY OF THE INVENTION According to one of its aspects, the inventionprovides a semiautomatic, precisely repeatable program controlledcasting method and apparatus which avoid the above-noted and otherdisadvantages inherent in the existing manual casting techniques. Tothis end, the present casting method and apparatus involve a number ofsuccessive programmed working and checking operations, including initialsemiautomatic startup operations and final fully automatic chamberpumpdown, melting, pouring, and shutdown operations. By way of example,a typical programmed casting cycle proceeds from initial conditioning ofthe casting apparatus for operation through loading of the metal chargeinto the crucible, evacuation of the vacuum chamber, checking of thechamber vacuum level, melting and superheating of the metal charge inthe crucible, preheating of the crucible pouring lip, checking of thechamber vacuum level and the temperature of the molten charge,uncovering the preheated mold, pouring of the molten charge, venting ofthe vacuum chamber, shutdown of the apparatus, and final return of theapparatus to its initial state in readiness for the next casting cycle.Each step or operation of the casting cycle must occur to propercompletion before the next operation can proceed. In some cases, thisrequires merely the performance of certain mechanical actions. In othercases, occurrence of an operation to proper completion requiresexpiration of a measured time delay. In yet other cases, propercompletion of an operation necessitates the attainment of apredetermined temperature level or vacuum level.

Certain operations of the present casting process proceed in accordancewith a preselected casting program which establishes the optimum castingparameters for the particular metal being cast, such as minimum chambervacuum level, alloying temperature, and pouring temperature. The programalso establishes other optimum parameters associated with the pouringoperation including the optimum pouring angle and angular velocityprofile of the crucible for the particular metal charge within thecrucible to obtain accurate entrance of the molten stream into the moldwith virtually no splash or contact of the molten metal with the rim ofthe mold.

According to one programming feature of the invention, the castingprocess is programmed with an information storage medium, such as aprogram card, which is coded to define a selected casting program. Anumber of these program cards, defining optimum casting programs fordifferent metals and/or cast shapes may be prepared for selectiveinsertion into the casting apparatus, depending upon the particularmetal to be poured and the cast shape to be produced. According toanother programming feature of the invention, the casting apparatus isprovided with a substitute or manual programmer which permits manualadjustment or setting of the individual casting parameters during a testprogram, to produce any desired casting program. This manual programmeris useful in determining, by the experimental process of trial anderror, an optimum casting program for a particular metal or shape to becast. The apparatus may also be equipped with certain manual overrideswitches to be selectively operated at any stage of the casting cycle toassume manual control of the cycle.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. I is a diagrammatic illustration of the present casting apparatus;

FIG. 2 is a circuit diagram of the control panel of the apparatus;

FIGS. 3a, 3b, and 3c are circuit diagrams of the apparatus;

FIG. 4 illustrates a casting program card for use in the castingapparatus;

FIG. 5 is a perspective view of a card reader employed in the castingapparatus;

FIG. 5a is an enlarged section through contacts of the card reader;

FIG. 6 is a circuit diagram of the card reader;

FIG. 7 is a circuit diagram of the card reader timing circuit;

FIG. 8 is a circuit diagram of the crucible drive controller;

FIG. 9 is a circuit diagram of the vacuum system for the vacuum castingchamber;

FIG. I0 is a circuit diagram of the temperature monitor;

FIG. I l is a circuit diagram of the heat controller;

FIG. 12 is a circuit diagram of the mold lid position controller; and

FIG. I3 is a circuit diagram of the manual programmer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is made first to FIG.1 diagrammatically illustrating a semiautomatic metal casting apparatus10 according to the invention. The casting apparatus includes a vacuumchamber 12 and vacuum pumping means 14 for evacuating the chamber.Exposed to the interior of the vacuum chamber is a vacuum level detector16 for sensing the vacuum level within the chamber. At the bottom of thechamber is a mold 18 supported on a mold positioning table 20. Acrucible 22, having an induction heating coil 23, is pivotally mountedover the mold and is coupled to a crucible tilt drive motor 25 forrotating the crucible through a range of angular positions. Associatedwith the mold I8 is a combination lid and positioning target 26 coupledto a lid operator 28. This operator may be actuated to move the mold lidbetween its broken and solid line positions of FIG. I. The solid lineposition of the lid is its retracted position, wherein the lid issituated to permit pouring of metal from the crucible 22 into the moldI8. The

broken line position of the lid is its target position, wherein the lidcloses the mold, which is preheated, to aid in retaining heat in themold and serves as a target for positioning the mold 18 properly toreceive molten metal from the crucible. At the top of the vacuum chamber12, over and in a position to view the interior of the crucible 22, isan optical thermal sensor 30. Access to the interior of the vacuumchamber 12 to introduce, position, and remove the mold l8 and to load ametal charge into the crucible 22 is provided by a door 32. This door,when closed, hermetically seals the chamber.

Operation of the casting apparatus is controlled by a semiautomaticcontrol system 34 powered from an electrical power supply 36. Thiscontrol system includes a programmer 38 into which may be inserted aninformation storage medium containing a preselected casting program, anda substitute or manual programmer 40 which may be operated manually toadjust the individual casting cycle parameters, thus to preset into thecontrol system any selected casting program. In the particularembodiment of the invention selected for presentation in thisdisclosure, the programmer 38 is designed to receive casting programcards which are prepared or coded to define difi'erent preselectedcasting programs. For this reason, the programmer 38 is hereinafterreferred to as a card programmer. It will be understood, however, thatother types of I information storage media may be utilized to store thepreselected casting programs. Also included in the control system is aprogram sequencer 42, a control panel 44, a crucible drive controller 45for the crucible drive motor 25, a vacuum controller 46 for the vacuumpumping means 14, a heat controller 48 for the crucible heating coil 23,a mold lid position controller 50 for the lid operator 28, and atemperature monitor 52 for the thermal sensor 30. A master controlcircuit 54 interconnects the several components of the casting apparatusto accomplish the semiautomatic casting or pouring cycle of theinvention. As noted earlier, this cycle involves a series of successiveworking and checking operations or steps, including preliminarysemiautomatic startup operations and subsequently fully automaticmelting, pouring, and shutdown operations. Certain of these operationsproceed in accordance with the casting program stored in the cardprogrammer 38 or preset into the manual programmer 40 in a manner suchthat the casting cycle occurs under the optimum conditions for theparticular metal being poured and shape being cast.

A detailed description of the casting apparatus 10 will be presentedshortly. In order to facilitate a full and complete understanding of thelater description, however, it is advisable to discuss at this point anexemplary casting cycle in step-by-step sequence.

It will become evident from the later description, that the castingcycle is caused to proceed from one step to the next by stepping of theprogram sequencer 42. Each step of the cycle must occur to propercompletion before the next step can occur. Accordingly, any malfunctionduring the casting cycle will automatically terminate the sequence untilthe malfunction is corrected. Moreover, as noted earlier and explainedin detail later, manual control of the casting cycle may be assumed atany point in the cycle. In the ensuing discussion of the casting cycle,reference is made to various programmed functions or parameters, such asprogrammed crucible positions and tilt speeds, programmed time delays,programmed temperatures, programmed heating power levels, and so on. Aswill appear from the later description, these are parameters which aredictated or established by the selected casting program inserted intothe card reader 38.

Attention is directed to the fact that the following steps define atypical casting program and are not to be construed as necessarilyoccuring in the order listed, as the order of seqbence is versatile andchangeable by simple resetting of the sequence order in the programmersequencer 42. Moreover, the actual steps involved in the casting cyclemay be varied by eliminating and/or adding steps.

PRECONDITION OF THE CASTING APPARATUS FOR AUTOMATIC CASTING OPERATIONAutomatic operation of the casting apparatus 10 requires the executionof certain preliminary manual operations to condition the apparatus forits automatic casting cycle which are represented in this disclosure byactuation of automatic mode switches 56, 58 on the control panel 44.These actions energize the control system 54 and produce a steppingimpulse which steps the program sequencer 42 from its initial or homeposition to initiate the first step of the casting cycle.

STEP l STEP 2 During this step of the casting cycle, bars or ingots ofthe metal to be cast are loaded into the crucible 22, and the mold lidoperator 28 is actuated manually by button 59 on the changeable panel 44to lower the mold lid 26 to its broken line target position of FIG. 1.In this regard, it should be noted that the mold lid is thus loweredonly after the mold 18 has been placed in the vacuum chamber 12 and thatthe act of lowering the lid is utilized, in effect, as a controlfunction to indicate the presence of the mold within the chamber.Arrival of the lid at its lower target position produces a steppingimpulse for stepping the program sequencer 42 to the third step of thecasting cycle.

STEP 3 STEP 4 This step is the final manual step of the casting cycleand involves closing and locking of the vacuum chamber door 32 tohermetically seal the vacuum chamber 12. Closing of the door produces astepping impulse which advances the program sequencer 42 to the fifthstep of the casting cycle. The latter step constitutes the beginning ofthe fully automatic portion of the casting cycle during which thesuccessive steps of the cycle occur automatically in sequence inresponse to proper completion of the preceding steps.

STEP 5 During this first automatic step of the casting cycle, the

vacuum controller 46 and the heat controller 48 are energized tocommence evacuation of the vacuum chamber 12 and condition the heatcontroller for the subsequent crucible heating step. The crucible drivecontroller 45 is activated to rotate the crucible 22 to a programmedmelt position. Relation of the crucible to this position produces astepping impulse for advancing the program sequencer 42 to the sixthstep of the casting cycle.

STEP 6 This step activates the vacuum level detector 16 to check thevacuum level in the vacuum chamber 12. When this vacuum level reaches aprogrammed heat-start vacuum level, a stepping impulse is produced whichadvances the program sequencer 42 to the seventh step of the castingcycle.

STEP 7 In this step, the heat controller 48 is activated to energize thecrucible heating coil 23 to programmed melt power level. Simultaneously,a programmed melt time delay is initiated and programmed superheattemperature information is fed to the temperature monitor 52. Theprogrammed melt time delay represents the approximate heating time, lessa selected fixed time interval such as one minute, required at theprogrammed melt power level to melt the metal charge within the crucible22 and bring the molten metal to a temperature level which is less, by apreselected temperature difference, than the programmed superheattemperature. At the expiration of the melt time delay, a steppingimpulse is produced to step the sequencer 42 to the eighth step ofthecasting cycle.

STEP 8 During this step, the crucible drive controller 45 is activatedto rotate the crucible 22 at a relatively slow creep rate to an uprightposition in which the molten metal in the crucible is exposed to thethermal sensor 30. Also, control of the heat controller 48 iseffectively transferred from the card programmer 38, which supplies theprogrammed melt power information for controlling the power levelsetting of the heat controller in step 7, to the temperature monitor 52.The temperature monitor activates the heat controller 48 to energize thecrucible heating coil 23 at a preselected full controlled power level.Simultaneously, an additional fixed melt time delay, equal to theselected time delay interval referred to in step 7, i.e. 1 minute, isinitiated. At the expiration of this fixed melt time delay, a steppingimpulse is produced to advance the sequencer to its ninth step.

STEP 9 This step involves resumption of control of the heat controller48 by the card programmer 38 and reduction of the power level setting ofthe heat controller to a programmed hold power level. After a shortdelay to permit thermal stabilization, the temperature monitor 52 isactivated to compare the temperature of the molten metal with theprogrammed superheat temperature level and to determine the heatingpower level required to heat the metal to the superheat temperature. Ifthe required heating power level is less than the programmed hold powerlevel, a forward stepping impulse is produced which advances the programsequencer 42 to the following lOth step of the casting cycle. On theother hand, if the required power level is greater than the hold powerlevel, a backstepping impulse is produced which returns the sequencer tothe preceding eighth step of the casting cycle to repeat the latter stepat controlled power level proportional to the temperature error. Afterexpiration of the fixed heating time delay of the eighth step, thesequencer is again advanced to repeat the ninth step. This procedure isrepeated, at a controlled heating power level which gradually drops asthe metal temperature increases, until the heating power level requiredto achieve the programmed superheat temperature closely approaches thehold power level, indicating an acceptable temperature error, whereuponthe sequencer advances to the 10th step.

STEP 10 In this step, the power level of the heat controller is reducedto a preset low level and the crucible drive controller 45 is activatedto rotate the crucible 22 at the creep rate to a programmed lip heatposition, wherein the molten metal within the crucible contacts but doesnot overflow the crucible pouring lip. Also, a programmed lip heat delayis initiated. This lip heat delay represents the time period required toheat the pouring lip at the power level to the proper pouringtemperature and cool the molten metal from its superheat temperature toa temperature slightly above, i.e. on the order of 25 above, aprogrammed pouring temperature of the metal. A stepping impulse isproduced at the expiration of the lip heat delay to advance thesequencer 42 to the 1 1th step of the casting cycle.

STEP 1 I In this step, the crucible 22 is returned at the creep rate toits upright position and the heat controller 48 is activated by thetemperature monitor 52 to energize the crucible heating coil at acontrolled power level proportional to the temperature error between themetal temperature and the programmed pouring temperature. A fixedheating delay, such as 1 minute delay is initiated, after which astepping impulse is produced to advance the sequencer 42 to the 12thstep.

STEP l2 This step again activates the temperature monitor 52 to read thetemperature of the molten metal within the crucible 22 after a briefdelay to permit thermal stabilization and to compare the temperature ofthe molten metal with its programmed pouring temperature. If thetemperature of the metal is less than its programmed pour temperature, abackstepping impulse is produced to return the sequencer 42 to its 11thstep to repeat the latter step at a power level proportional to thetemperature error. If the metal temperature exceeds the programmed pourtemperature on the other hand, the system waits, applying heating powerto the crucible at a preset minimum power level, until the metaltemperature cools to the programmed pour temperature. When the exactpour temperature is attained, a stepping impulse is produced to advancethe sequencer 42 to its 13th step.

STEP 13 This step returns the heat controller 48 to its programmed holdpower level and verifies the existence of a programmed minimum pourvacuum level within the vacuum chamber 12. A stepping impulse is thenproduced to step the sequencer 42 to the following 14th step of thecasting cycle.

STEP l4 During this step, the mold lid operator 28 is actuated by themold lid position controller 50 to raise the mold lid 26 to its solidline retracted position of FIG. 1. The crucible drive controller 45 isactuated to rotate the crucible 22 to a final programmed pour angle at aprogrammed pour speed which is selected to cause entrance of the moltenstream into the mold 18 with virtually no splash or contact of themolten metal with the rim of the mold. Rotation of the crucible to itsfinal pouring position produces a stepping impulse for advancing thesequencer 42 to the final 15th step of the casting cycle.

STEP 15 This step is a cooling step during which all heating power tothe crucible is turned ofi, and a programmed vent delay time isinitiated. This vent delay time represents the time required for coolingof the poured metal under vacuum within the mold 18 to a selectedreduced temperature. At the expiration of the delay, a stepping impulseis produced to advance the programmed sequencer 42 to its initial homeposition. Return of the sequencer to its home position cuts power to thevacuum and heat controllers 46, 48 to shutdown the vacuum pumping system14 and automatically vent the vacuum chamber 12 to atmosphere andthereby complete the casting cycle.

The casting apparatus 10 of the invention which has been selected forillustration will now be described in greater detail by initialreference to FIG. 3. In the ensuing description, programmed controlinfonnation is referred to in terms which connote the functions to whichthe information relates. For example, programmed information relating toa crucible position is referred to as angle select information. Meltangle selection information, for instance, is programmed crucibleposition information which dictates the angular position in which thecrucible 22 is to be located during the melt phase of the casting cycle.Programmed information relating to heating power level, temperatures,time delays, crucible tilt rate, etc., is referred to in similar terms.Pour temperature select information, for example, is control informationwhich dictates a preselected temperature at which the molten metal is tobe poured. As it will appear from the later description, this controlinformation is electrical information in the form of voltage signals. Ina similar manner, certain mechanical elements of the casting apparatusare referred to in terms which indicate the functions performed by therespective elements. By way of example, a melt angle select switch isreferred to in the ensuing description. This is a switch for feedingmelt angle select information from the card programmer 38 to thecrucible drive controller 24. It will be understood, of course, that thevarious functions referred to in the description are those mentioned inthe earlier discussion of the casting cycle.

Turning now to FIG. 3, the illustrated program sequencer 42 is a rotarystepping drum-type sequencer, such as that marketed by the Tenor Companyof Milwaukee, Wis., under the name Tenor Programmer. This sequencer isdiagrammatically illustrated in FIG. 3 as comprising a number ofswitches 60, a rotary drum 62 having changeable pins 63 for actuatingthe switching in a desired sequence as the drum rotates, and anelectrical stepping actuator 64 for rotating the drum in stepwisefashion through a number of successive positions or steps. In thisinstance, the sequencer drum 62 uses 16 positions or steps correspondingto the initial conditioning step and working steps of the casting cycledescribed earlier. Fewer or additional steps may be employed, dependingupon the number of steps in the casting cycle.

In connection with actuation of the sequencer switches 60 by thesequencer drum 62, it will appear from the ensuing description that eachswitch has a normal position and a second position to which the switchis operated by the drum. In some cases, the drum may operate a switch inonly one drum stepping position. In other cases, the drum may operate aswitch in a number of stepping positions, either consecutive steppingpositions or spaced stepping positions. The switch operating pins 63 onthe drum may be so arranged that a switch which is operated in a numberof consecutive stepping positions remains in its drum actuated positioncontinuously throughout these positions including the intervals duringwhich the drum steps from one position to the next. Attention isdirected to the bracketed numerals below the broken lines representingthe drum pins 63 in FIG. 3. These numerals identify the steppingposition or positions of the drum in which the corresponding drum switch60 is actuated.

Power supply 36 provides both AC and DC power for operating the castingapparatus in the manner explained in the ensuing description. In thisregard, attention is directed to the fact that the casting apparatus andits operation are described below in relation to the typical orexemplary casting cycle discussed earlier. Accordingly, it should beunderstood that the invention contemplates within its scope variousmodifications, which will become obvious as the description proceeds, toaccommodate variations in the casting cycle.

The stepping actuator 64 of program sequencer 42 has two normally openswitches 72, 76 and opens a normally closed switch 74. Switch 72 is aload angle select switch. This switch, when closed, completes a circuitfrom a load angle select terminal of the card programmer 38 through alead 80, the switch contacts, and a lead 82 to the crucible drivecontroller 45. As it will appear from the later description, thiscircuit is utilized to feed programmed load angle information to thedrive controller for energizing the crucible drive motor 25 to rotatethe crucible 22 to a programmed loading position. Sequencer switch 74 isa creep relay switch. This switch, when closed, completes an energizingcircuit from a low voltage lead 83 of the power supply 36 through a lead84, the switch contacts, and a lead 86 to the crucible controller 45 forenergizing a creep relay within the controller. As explained later, thecreep relay, when thus energized, conditions the drive controller toenergize the crucible drive motor at a relative slow creep rate inresponse to angle select information, such as the load angle selectinformation just mentioned, for rotating the crucible 22 at this rate tothe position represented by the information. Programmer switch 76 is anautomatic power-on check switch. This switch, and a set of normally opencontacts 56a are connected in electrical series between the low voltagesupply lead 83 and the sequencer forward stepping lead 68. Closure ofthe contacts 56a thus applies a forward stepping voltage to the programsequencer 42 which steps the latter from its home position H to itsfirst stepping position. As will be explained presently, contacts 560are contacts of the automatic mode switch 56 on the control panel 44which are closed by actuation of the switch. Actuation of switch 58energizes the control system including lead 83 from the power supply 36.Thus, actuation of both switches conditions the casting apparatus forits casting cycle and steps the sequencer from its home position to itsfirst stepping position.

As indicated in FIG. 3, the load angle select switch 72 remains closedfrom the home position H through the fourth stepping position and isthen reclosed from the l5th stepping position back to the home positionH of the sequencer 42. Creep relay switch 74 is open in the homeposition of the sequencer and closes to energize the creep relay whenthe sequencer advances to its first stepping position. The switchreopens to deenergize the creep relay in the l3th and l4th steppingpositions. The automatic power-on check switch 76 is closed only in thesequencer home position and opens when the sequencer steps from thisposition.

It is now evident that actuation of the switches 56, 58 in the homeposition of the sequencer 42 feeds programmed crucible load angleinformation from the card programmer 38 to the crucible drive controller45, supplies operating power to the control system and closes thesequencer stepping contacts 560 to advance the program sequencer 42 toits first stepping position.

Stepping of the program sequencer 42 to its first stepping positioncloses the creep relay switch 74 to energize the creep relay in thecrucible drive controller 45. The programmed crucible load angleinformation which is currently being fed to the controller through theclosed sequencer load angle select switch 72 then actuates thecontroller to drive the crucible 22 at the creep rate to the programmedload angle. In its first stepping position, the sequencer 42 also closesa normally open MLC (main line contactor) check switch 90. Switch 90 anda set of nonnally open contacts 920 are connected in electrical seriesbetween the supply lead 83 and the sequencer forward stepping lead 68.Accordingly, closure of the contacts 92a applies a forward steppingvoltage to the sequencer 42 which steps the latter from its firststepping position to its second stepping position. Contacts 92a arecontacts of an MLC (main line contactor) relay embodied in the heatcontroller 48. As explained later, this relay is energized to close itscontacts upon proper completion of the precondition steps at the outsetof the casting cycle. Accordingly, if these precondition steps have beenproperly completed, closure of the MLC check switch 90 by the sequencerdrum 62 upon stepping of the latter to its first position results inimmediate stepping of the drum to its second stepping position. The MLCcheck switch reopens upon stepping of the drum.

From the earlier description of the typical casting cycle, it will berecalled that in the second step of the cycle, the mold lid 26 islowered to its broken line position of P16. 3 to signify that the mold18 has been placed in the vacuum chamber 12 and to permit use of the lidas a target for placement of the mold in proper pouring positionrelative to the crucible 22. Arrival of the lid in its lower targetposition closes a normally open lid-down limit switch 94 actuated by themold lid operator. Switch 94, and a normally open switch 96 of theprogram sequencer 42 are connected in electrical series between the lowvoltage supply lead 83 and the sequencer forward stepping lead 68.Sequencer switch 96 is a lid-down check switch which is closed in thesecond stepping position of the sequencer. Thus, with the sequencer inits second stepping position, lowering of the mold lid 26 to its targetposition applies a forward stepping voltage to the sequencer which stepsthe latter to its third stepping position. The lid-down check switch 96reopens when the sequencer steps.

In the third stepping position of the program sequencer 42, the cardprogrammer 38 is opened and a previously prepared casting program cardis inserted. In FIG. 3, the card programmer is diagrammaticallyillustrated as having a hinged cover 100 which may be rotated to openposition for insertion of the program card. After the card has beenproperly inserted into the programmer, the latter is closed by rotationof its cover 100 to closed position. The card programmer 38 and thecasting program card will be described in detail presently. Suffice itto say at this point that the card programmer embodies normally openswitches 102, 103 which are closed by proper placement of a program cardin the programmer and by closure of the programmer cover 100,respectively. These switches and a normally open switch 104 in theprogram sequencer 42 are connected in electrical series between thesupply lead 83 and the sequencer forward stepping lead 68. Switch 104 isa normally open card programmer check switch which closes in response tostepping of the sequencer to its third stepping position. It is nowevident, therefore, that insertion of a program card into the cardprogrammer 38 and closure of the latter with the program sequencer 42 inits third stepping position applies a forward stepping voltage to thesequencer which steps the sequencer to its fourth stepping position.

Stepping of the sequencer 42 to its fourth stepping position closes anormally open vacuum chamber door check switch 106. Switch 106 and aswitch 108 are connected in electrical series between the supply lead 83and the sequencer forward stepping lead 68. Switch 103 is operated bythe door 32 of the vacuum chamber 12 in such a way that the switchcloses when the door is closed to seal the chamber. Thus, closure of thechamber door 32 during the fourth step of the casting cycle steps theprogram sequencer 42 to its fifth stepping position. In this regard, itis significant to recall that the first four steps of the casting cyclerequire manual operations for their completion. The remaining steps ofthe cycle, commencing with step number 5, are fully automatic.

Stepping of the sequencer 42 to its fifth stepping position closes anormally open switch 110 which is hereinafter referred to as avacuum-heat controller switch. One terminal of this switch is connectedto the low voltage power supply lead 83. The other terminal of theswitch is connected through a lead 1 13 to the vacuum controller 46 andheat controller 48. Accordingly, closure of the vacuum-heat controlleron switch 110 in stepping position of the program sequencer 42 connectsthe vacuum and heat controllers to the supply lead 83. The vacuum andheat controllers will be described in detail presently. Suffice it tosay at this point that connection of the controllers to the supply lead83 activates the controllers. The vacuum controller 46, when thusactivated, immediately energizes the vacuum pumping means 14 to commenceevacuation or pump-down of the vacuum chamber 12. The heat controller48, when activated, on the other hand, is merely conditioned to energizethe crucible heat coil 23. In this regard, it will be seen that the MLCcontacts in the heat controller, which were closed at the start of thecasting cycle, are reopened in response to activation of the heatcontroller at this point to open the energizing circuit between thecontroller and the heating coil. The MLC contacts are reclosed toenergize the coil in the seventh step of the sequencer. It issignificant to note here that the sequencer switch remains closed, andhence the vacuum and heat controllers remain in their activated or oncondition, from the fifth stepping position through the 15th steppingposition of the program sequencer 42.

Stepping of the program sequencer 42 to its fifth stepping position alsoclosed a pair of normally open switches 114 and 116. Switch 114 is amelt-angle select switch which completes a circuit from a melt-angleterminal of the card programmer 38, through a lead 118, the switchcontacts, and a lead to the lead 82 extending to the crucible drivecontroller 45. As will appear presently, this circuit is utilized tofeed a programmed crucible melt-angle signal from the card programmer tothe crucible drive controller. This signal activates the controller toenergize the crucible drive motor 25 for rotating the crucible 22 at itscreep rate from its current loadangle position to the programmedmelt-angle position. The melt-angle select switch 114 remains closed, sothat the crucible remains in its programmed melt-angle position, fromthe fifth stepping position through the seventh stepping position'of theprogram sequencer 42.

Associated with the crucible drive system is a normally open switch 121which is momentarily closed in response to rotation of the crucible 22from its load angle position to its meltangle position as well as inresponse to later rotation of the crucible to its pour-angle position.In the particular embodiment of the invention selected for illustration,the switch 121 closes in response to rotation of the crucible through an80 position (i.e. a position displaced 80 from the horizontal and 10from the vertical). For this reason, the switch 121 is referred to forconvenience as an 80 switch. The 80 switch 121 and a fixed delay timer122 are connected in electrical series to the supply lead 83 so thatclosure of the switch energizes the timer to commence running of a fixeddelay time to be discussed presently. The timer has normally opencontacts 122a in series with a sequencer switch 116 which closes in thefifth stepping position. At the expiration of its fixed delay, timercloses its contacts to connect lead 83 to the sequencer forward steppinglead 68. Closure of the 80 switch 121 in response to rotation of thecrucible 22 through its 80 position with the sequencer in its fifthstepping position thus applies a forward stepping voltage to thesequencer for advancing the latter to its sixth stepping position.

As noted in FIG. 3 of the drawings, sequencer switch 116, hereinafterreferred to as an 80 stepping switch, opens upon stepping of thesequencer and subsequently recloses in the 14th stepping position of thesequencer.

lt is now evident, therefore, that stepping of the program sequencer 42to its fifth stepping position turns on the vacuum controller 46 tocommence pumpdown of the vacuum chamber 12 and turns on the heatcontroller 48 to condition the latter for energizing the crucibleheating coil 23 in the seventh step of the sequencer. The crucible drivecontroller 45 is also activated to drive the crucible 22 from itsprogrammed load-angle position to its programmed melt-angle position.Rotation of the crucible through its 80 position on its way to itsmelt-angle position advances the program sequencer 42 to its sixthstepping position.

In the sixth stepping position of the program sequencer 42, a normallyopen vacuum-step switch 124 is closed. This switch completes a steppingcircuit from a vacuum-step terminal of the card programmer 38, through alead 126 and the switch contacts to the sequencer forward stepping lead68. As will appear from the later description, the chamber vacuum leveldetector 16 and the card programmer 38 cooperate to produce a steppingvoltage at the latter programmer terminal in response to reduction ofthe pressure within the vacuum chamber 12 to or below a programmedheat-start vacuum level. This stepping voltage is applied to thesequencer stepping lead 68 through the circuit 124, 126 to step thesequencer 42 to its seventh stepping position. In this regard, it issignificant to recall that evacuation of the vacuum chamber 12 commencesin the preceding stepping position of the sequencer 42 by closure of itsvacuum-heat controller on switch 1 10.

From the foregoing discussion, it will be understood that in the sixthstepping position of the program sequencer 42, the vacuum chamber 12 ispumped down by the vacuum pumping means 14, thereby reducing thepressure within the chamber. When the vacuum chamber is finallyevacuated at least to the programmed heat start vacuum level, thesequencer 42 is advanced to its seventh stepping position.

Stepping of the program sequencer 42 to its seventh stepping positioncloses a group of five normally open switches 130, 132, 134, 136, and138. Switch 130 is a heating power-on switch which completes a circuitfrom the low voltage power supply lead 83 through the switch contactsand a lead 140 to the heat controller 148. As will appear from the laterdescription, the voltage which is thus applied to the heat controllerrecloses the MLC contacts in the heat controller to energize thecrucible heating coil 23. The switch 130 remains closed through the 14thstepping positions of the sequencer. Sequencer switch 132 is a meltpower select switch. Closure of this switch completes a circuit from amelt power terminal of the card programmer 38 through a lead 142, theswitch contacts, and a lead 144 to the heat controller 48. From thelater description, it will be seen that a programmed melt power levelsignal is thereby fed from the card programmer 38 to the heat controller48. This signal adjusts the controller to energize the crucible heatingcoil 23 at the programmed melt power level. Switch 132 opens in responseto stepping of the sequencer 42 to its next stepping position. The thirdswitch 134 to be closed in the seventh stepping position of thesequencer 42 is a superheat temperature select switch which remainsclosed through the ninth stepping position. Closure of this switchcompletes a circuit from a superheat temperature terminal of the cardprogrammer 38, through a lead 146, the switch contacts, and a lead 148to the temperature monitor 52. A programmed superheat temperature signalis thereby fed from the card programmer 38 to the monitor to be utilizedin the manner explained below.

The two remaining switches 136 and 138 which close in the seventhstepping position of the program sequencer 42 are utilized to effect atiming function. Thus, switch 136 is a heating time delay start switchhaving one terminal connected to the power supply lead 83. The otherterminal of the switch is connected through a lead 150 to a melt timedelay power terminal of the card programmer 38. Closure of the switch136 energizes a timing circuit embodied in the card programmer tocommence running of a programmed melt time delay, as explained later. Atthe expiration of this delay, the timing circuit produces a steppingvoltage at a melt time delay step terminal of the card programmer. Thisstepping voltage is applied to the sequencer stepping lead 68 through alead 152 and the currently closed sequencer switch 138 to advance thesequencer to its eighth stepping position. This latter switch ishereinafter referred to as a time delay stepping switch. It will benoted that the melt time delay start switch 136 is closed only in theseventh stepping position of the sequencer 42, while the time delaystepping switch 138 is closed in stepping positions Nos. 7, l0, and 15.

From the foregoing description. it will be understood that the seventhstepping position of the program sequencer 42 energizes the crucibleheating coil 23 to a programmed melt power level to commence melting ofthe metal within the crucible 22. Simultaneously, programmed superheattemperature information is fed to the temperature monitor 52 and aprogrammed melt time delay is started. The length of this delay isselected to equal the time duration, less a fixed time interval oftypically 1 minute duration, required to melt the metal charge in thecrucible and heat the molten metal to a temperature on the order of lessthan the programmed superheat temperature. At the expiration of the melttime delay, the sequencer 42 is advanced to its eighth steppingposition.

In its eighth stepping position, the sequencer 42 closes a normally openswitch 154. Closure of this switch completes a circuit from the powersupply lead 83 through the switch contacts and a lead 156, to a fixeddelay timer 158 having normally open contacts 1580. A voltage is therebyapplied to the timer to commence running of a fixed time delay. At theexpiration of this delay, which is equal to the fixed time interval,i.e. l minute, referred to in the preceding stepping position of thesequencer 42, the timer contacts 158a close. These timer contacts areconnected in electrical series between the supply lead 83 and thesequencer stepping lead 68. Accordingly, closure of the timer contactssteps the sequencer 42 to its ninth stepping position. Lead 156 alsoextends to the temperature monitor 52. Accordingly, a voltage is appliedto the monitor concurrently with energizing of the fixed delay timer158. As will be explained presently, this voltage and the programmedsuperheat temperature signal which is currently being applied to thetemperature monitor through the sequencer switch 134 cooperate to effectelectrical connection of the temperature monitor to the heat controller48 and actuation of the monitor to transmit a programmed heating powerlevel signal from a full controlled power level terminal of the cardprogrammer 38, through a lead 1590 the temperature monitor. and a lead15% to the heat controller. This power level signal, hereafter referredto as a full controlled power level signal, adjusts the heat controllerto energize the crucible heating coil 23 at the programmed fullcontrolled power level. As will appear from the later description, theabove actuation of the temperature monitor 52 in response to closure ofthe sequencer switch 154 involves a controlled power level lockingfunction in the monitor. For this reason, the switch is hereafterreferred to as a controlled power level lock switch or simply a powerlock switch.

ln the eighth stepping position of the sequencer 42, then, the crucibleheating coil 23 is energized at the programmed full controlled powerlevel for a fixed period of time, in this instance l minute. Thesequencer 42 then advances to its ninth stepping position. The powerlock switch 154 reopens when the sequencer steps and subsequentlyrecloses in the 11th sequencer stepping position. Reopening of switch154 deenergizes the fixed delay timer 158, which then resetsautomatically in readiness for its next timing cycle, and disconnectsthe temperature monitor 52 from the heat controller 48 to terminateenergizing of the heating coil 23 at the full controlled power level.

In its ninth stepping position, the program sequencer 42 closes a pairof normally open switches and 162. Switch 160 is a hold power levelselect switch which reopens when the sequencer steps and subsequentlyrecloses in the 13th and 14th stepping positions. Closure of this switchcompletes a circuit from a hold power level tenninal of the cardprogrammer 38, through a lead 164, the switch contacts, and a lead 166and the lead 144 to the heat controller 48. As will be explained later,a programmed hold power level signal is thereby fed from the cardprogrammer 38 to the heat controller 48. This signal adjusts the heatcontroller to energize the crucible heating coil 23 at the programmedhold power level which is selected to produce a crucible heatingtemperature approximating a programmed pouring temperature of the moltenmetal in the crucible. Sequencer switch 162 is a temperature interrogateswitch which closes in the ninth stepping position only to complete acircuit from the power supply lead 83 through the switch contacts and alead 168 to a fixed delay timer 170 having normally open contacts 1700.Accordingly, closure of the switch 162 energizes the timer to commence afixed time delay. At the expiration of this delay, the timer contacts170a close to connect the lead 168 to a lead 172 extending to thetemperature monitor 52. As explained later, the voltage signal which isthus applied to the temperature monitor 52 effectively interrogates themonitor to determine the heating power level required to heat the moltenmetal in the crucible to its programmed superheat heat temperature. Thefixed delay introduced by the timer 170 permits stabilization of thetemperature monitoring system. Extending from the temperature monitorare leads 174 and 176. Lead 174 connects to the forward stepping lead 68and lead 176 to the backstepping leads 70 of the program sequencer 42.As will also appear from the later description, the temperature monitor52 responds to the incoming interrogate signal by applying a forwardstepping voltage to the lead 174 if the required heating power level isless than the programmed hold power level and a backstepping voltage tothe lead 176 if the required power level exceeds the hold power level.

it will now be understood that in the ninth stepping position of thesequencer 42, the temperature monitor 52 is interrogated concerning theheating power level required to heat the molten metal within thecrucible 22 to its programmed superheat temperature. If the requiredheating power level change exceeds 50 percent of the programmed fullcontrolled power level, the sequencer is returned to its eighth steppingposition to repeat the l-minute heating step of this position. Asexplained later, however, during this reheating step, the crucibleheating coil 23 is energized at a controlled power level proportional tothe temperature error between the programmed superheat temperature andthe actual metal temperature. On the other hand, if the required heatingpower is less than 50 percent of the full controlled power level, thesequencer is advanced to its th stepping position.

In its 10th stepping position, the sequencer 42 closes three normallyopen switches 178, 180, and 182. Switch 178 is a lip heat angle selectswitch. Closure of this switch completes a circuit from a lip heat angleterminal of the programmer 38, through a lead 184, the switch contacts,lead 186 and the lead 82 to the crucible drive controller 24. From thelater description, it will appear that this action feeds a programmedlip heat angle signal from the card programmer 38 to the crucible drivecontroller 24. The drive controller energizes the crucible drive motor25 in response to this signal to rotate the crucible 22 at its slowcreep rate to a programmed lip heat angle position. In this position,the molten metal within the crucible contacts but does not overflow thecrucible pouring lip. Switch 180 is a lip heat delay start switch.Closure of this switch connects the power supply lead 83 to a lip heatdelay power terminal of the card programmer 38 through the switchcontacts and a lead 188. A voltage is thereby applied to the cardprogrammer which activates the timing circuit in the programmer togenerate a programmed lip heat delay time. This lip heat delay isselected to equal the time duration, less a fixed time interval such as1 minute, required to heat the crucible pouring lip to the properpouring temperature and cool the molten metal in the crucible from itscurrent superheat temperature to a temperature slightly above, typicallyon the order of 25 F. above, a programmed pouring temperature. In thisregard, it is significant to note that in the 10th stepping position, noheating power level signal is supplied to the heat controller 48. Aswill be seen later, under these conditions, the heat controllerenergizes the crucible heating coil 23 at a reduced power level whichpermits cooling of the metal as just stated. Switch 182 is a pourtemperature select switch which remains closed through the 12th steppingposition. Closure of this switch completes a circuit from a pourtemperature terminal of the card programmer 38 through a lead 189, theswitch contacts, a lead 190 and the lead 148 to the temperature monitor52. Programmed pour temperature signal is then fed from the cardprogrammer to the monitor to be utilized in the manner explained below.

At the expiration of the programmed lip heat delay, which commences torun in response to closing of the sequencer lip heat delay start switch180, the timing circuit in the card programmer 38 produces a sequencerstepping voltage at a lip heat delay step terminal of the programmer.This terminal is connected through a lead 191 and the lead 152 to thetime delay step switch 138 of the sequencer 42. It will be recalled thatthis switch closes in the 10th stepping position of the sequencer.Accordingly, the stepping voltage produced by the card programmeradvances the sequencer to its l lth stepping position.

It will now be understood that in the 10th stepping position of thesequencer 42, the heating power level of the crucible 22 is reduced tothe programmed hold power level, the crucible is reduced, the crucibleis rotated to a programmed lip heat angle to heat the crucible pouringlip and cool the molten metal within the crucible to a temperatureslightly above a programmed pouring temperature, and a programmed pourtemperature signal is fed to the temperature monitor. At the expirationof the programmed lip heat delay, the sequencer 42 is advanced to its 1lth stepping position.

In its llth stepping position, the program sequencer 42 recloses thecontrolled power lock switch 154 for the heat controller 48 andreenergizes the fixed delay timer 158 to commence running of the fixed,i.e. 1 minute, delay. Closure of switch 154 returns control of the powerlevel setting of the heat controller 48 to the temperature monitor 52which is currently being supplied with a programmed pour temperaturesignal from the card programmer. The heat controller is then adjusted toenergize the crucible heating coil 23 at a controlled power levelproportional to the temperature error between the temperature of themolten metal and the programmed pour temperature.

From the preceding discussion, it will be understood that in the l lthstepping position of the program sequencer 42, the crucible heating coil23 is energized at a controlled power level, proportional to thetemperature error between the molten metal temperature and theprogrammed pour temperature for a fixed heating delay time, i.e. 1minute. At the expiration of this fixed delay, the sequencer 42 isadvanced to its 12th stepping position.

Stepping of the program sequencer 42 to its 12th stepping positioncloses a normally open temperature interrogate switch 196. Closure ofthis switch connects a fixed delay timer 198 to the power supply lead 83through a lead 200 and the switch contacts. The timer is thus energizedby closing of the switch 196 to commence running of a fixed time delay.This time delay is selected to permit thermal stabilization of thetemperature monitoring system. At the expiration of the fixedstabilization delay, the timer contacts 1980 close to connect the powersupply lead 83 to the temperature monitor 52 through the lead 200 and alead 202. As will be explained later, the voltage thus applied to thetemperature monitor conditions the latter to compare the temperature ofthe molten metal within the crucible 22 to the programmed pourtemperature and to generate a sequencer backstepping voltage, forwardstepping voltage, or no stepping voltage depending upon therelationships of these temperatures. Thus, if the metal temperature isless than the programmed pour temperature, the temperature monitorgenerates a backstepping voltage which is applied through the lead 176to the sequencer backstepping lead 70. Under these conditions theprogram sequencer 42 returns to the proceeding 1 lth stepping positionto repeat the fixed time heating step of that position at a heatingpower level proportional to the temperature error between the actualmetal temperature and the programmed pour temperature. If the metaltemperature exactly equals the programmed pour temperature, thetemperature monitor 52 generates a forward stepping voltage which isapplied through the lead 174 to the sequencer forward stepping lead 68to advance the sequencer 42 to its 13th stepping position. Finally, ifthe metal temperature exceeds the programmed pour temperature, thetemperature monitor produces no stepping voltage until the molten metalcools to the exact programmed pour temperature. When this occurs, thetemperature monitor produces a forward stepping voltage for advancingthe sequencer 42 to its 13th stepping position, as just explained.

1. Automatic casting apparatus comprising: a crucible for containing ametal to be cast; a motor for driving said crucible through a range ofangular positions; an induction heater for heating said metal to themolten state; means for sensing and generating a signal related to theangular position of said crucible; means for sensing and generating asignal representing the temperature of the molten metal in saidcrucible; programmer means including means for storing informationproviding a casting program representing preselected program parametersincluding melt and pour angles for said crucible, a heating power levelfor said heater, and a metal pouring temperature and selectivelyactuable means for reading said parameters in sequence in response tosuccessive actuations of said programmer means and producing a signalrepresenting each parameter; and automatic control means including meansfor operating said motor and heater in response to said signals andmeans for actuating said programmer means to advance said program fromone parameter to the next at the completion of each operation inresponse to a parameter signal to cause said apparatus to proceedthrough an automatic casting cycle involving initial operation of saidmotor in response to the melt angle signal to drive said crucible tosaid melt angle, operation of said heater in response to the heatingpower level signal to heat said metal to the molten state at saidheating power level while said crucible occupies said melt angle and tothereafter heat the molten metal to said pouring temperature in responseto the pouring temperature signal, and operation of said motor inresponse to the pour angle signal following heating of the molten metalto said pouring temperature to rotate said crucible to said pour angle.2. Automatic casting apparatus according to claim 1, wherein: saidprogram parameters include a parameter representing a rate of rotationof said crucible to said pour angle; said programmer means produces atilt rate signal representing said rotation rate; means for sensing andgenerating a signal representing the rotational speed of said crucible;and said control means operates said motor in response to said signalsto cause rotation of said crucible to said pour angle at said rotationrate.
 3. Automatic casting apparatus according to claim 1, wherein: saidcrucible has a pouring lip; said program parameters include a parameterrepresenting a lip heat angle for said crucible wherein the molten metalwithin the crucible contacts but does not overflow said pouring lip anda parameter representing a lip heat delay time; said programmer meansproduces a signal representing said lip heat angle and a signalrepresenting said lip heat delay time; and said control means operatessaid motor in response to said signals to rotate said crucible to andretain the crucible at said lip heat angle for said lip heat delay timefollowing heating of said metal to the molten state and prior torotation of said crucible to said pour angle, thereby to heat said lipprior to pouring of the molten metal.
 4. Automatic casting apparatusaccording to claim 3, wherein: said program parameters include aparameter representing a superheat temperature in excess of said pouringtemperature; said programmer means produces a signal representing saidsuperheat temperature; and said control means opeRates said heater inresponse to said signals to heat said metal to the molten state and thenheat the molten metal to said superheat temperature while said crucibleoccupies said melt angle and to thereafter bring the temperature of themolten metal to said pouring temperature following heating of saidcrucible pouring lip.
 5. Automatic casting apparatus according to claim3, wherein: said control means includes means for operating said heaterat a reduced heating power level during heating of said pouring lip; andsaid superheat temperature, lip heat delay time, and reduced power levelare selected to effect heating of said pouring lip to a given liptemperature and concurrent cooling of said molten metal approximately tosaid pouring temperature.
 6. Automatic casting apparatus according toclaim 1, wherein: said program parameters include a parameterrepresenting an initial temperature of said molten metal and a parameterrepresenting a heating delay time at said heating power level requiredto heat the molten metal to a selected temperature less than saidinitial temperature; said programmer means produces a signalrepresenting said initial temperature and a signal representing saidheating delay time; and said control means includes means for operatingsaid heater in response to said power level signal to initially heatsaid metal at said heating power level for said heating delay time,heating said metal for an additional fixed delay time, and thenalternately comparing the temperature of said molten metal to saidinitial temperature and heating said metal for said fixed delay time ata power level related to the temperature error between the metaltemperature and said initial temperature until the temperature of themolten metal approximately equals said initial temperature, all prior torotation of said crucible to said pour angle.
 7. Automatic castingapparatus according to claim 6, wherein: said crucible has a pouringlip; said program parameters include a parameter representing a lip heatangle of said crucible wherein the molten metal within the cruciblecontacts but does not overflow said pouring lip and a parameterrepresenting a lip heat delay time; said programmer means produces asignal representing said lip heat angle and a signal representing saidlip heat delay time; said control means includes means for operatingsaid heater at a reduced heating power level during heating of saidpouring lip; said control means operates said motor in response to saidsignals to rotate said crucible to and retain the crucible at said lipheat angle for said lip heat delay time following heating of said metalto the molten state and prior to rotation of said crucible to said pourangle, thereby to heat said lip prior to pouring of the molten metal;said initial temperature is a superheat temperature in excess of saidpouring temperature; and said superheat temperature, lip heat delaytime, and reduced power level are selected to effect heating of saidpouring lip to a given lip temperature and concurrent cooling of saidmolten metal approximately to said pouring temperature.
 8. Automaticcasting apparatus according to claim 7, wherein: said control meansincludes means for comparing the temperature of the molten metal to saidpouring temperature and operating said heater to bring said molten metalto said pouring temperature after expiration of said lip heat delay. 9.Automatic casting apparatus according to claim 8, wherein: said programparameters include a parameter representing a rate of rotation of saidcrucible to said pouring angle; said programmer means produces a signalrepresenting said rotation rate; means for sensing and generating asignal representing the rotational speed of said crucible; and saidcontrol means operates said motor in response to said signals to rotatesaid crucible from said upright position to said pour angle at saidrotaTion rate.
 10. Automatic casting apparatus comprising: a vacuumchamber; vacuum pumping means for evacuating said chamber; a vacuumlevel detector for producing signals related to the vacuum level withinsaid chamber; a crucible within said chamber for containing a metal tobe cast; a motor for driving said crucible through a range of angularpositions; means for sensing and generating a signal representing theangular position of said crucible; an induction heater for heating saidmetal to the molten state; means for sensing and generating a signalrepresenting the temperature of the molten metal in said crucible;programmer means including means for storing information providing acasting program representing preselected program parameters including aheat start vacuum level for said chamber, melt and pour angles for saidcrucible, a heating power level for said heater, and a metal pouringtemperature, and selectively actuable means for reading said parametersin sequence in response to successive actuations of said programmermeans and producing a signal representing each parameter; and controlmeans including means for operating said motor and heater in response tosaid signals and means for actuating said programmer means to advancesaid program from one parameter to the next at the completion of eachoperation in response to a parameter signal to cause said apparatus toproceed through an automatic casting cycle involving initial operationof said pumping means to evacuate said chamber, operation of said motorin response to the melt angle signal to drive said crucible to said meltangle, operation of said heater in response to the heating power levelsignal to heat said metal to the molten state at said heating powerlevel while said crucible occupies said melt angle and thereafter heatthe molten metal to said pouring temperature in response to the pouringtemperature signal, and operation of said motor in response to the pourangle signal following heating of the molten metal to said pouringtemperature to rotate said crucible to said pour angle.
 11. Automaticcasting apparatus according to claim 10, wherein: said programparameters include a parameter representing a pour vacuum level for saidchamber; said programmer means produces a signal representing said pourvacuum level; and said control means operates said motor in response tosaid signals to rotate said crucible to said pour angle followingheating of said metal to said pour temperature and reduction of thechamber pressure to said pour vacuum level.
 12. Automatic castingapparatus according to claim 10, wherein: said program parametersinclude a parameter representing a rate of rotation of said crucible tosaid pour angle; said programmer means produces a signal representingsaid rotation rate; means for sensing and generating a signalrepresenting the rotational speed of said crucible; and said controlmeans operates said motor in response to said signals to cause rotationof said crucible to said pour angle at said rotation rate.
 13. Automaticcasting apparatus according to claim 10, wherein: said crucible has apouring lip; said program parameters include a parameter representing alip heat angle for said crucible wherein the molten metal within thecrucible contacts but does not overflow said pouring lip and a parameterrepresenting a lip heat delay time; said programmer means produces asignal representing said lip heat angle and a signal representing saidlip heat delay time; and said control means operates said motor inresponse to said signals to rotate said crucible to and retain thecrucible at said lip heat angle for said lip heat delay time followingheating of said metal to the molten state and prior to rotation of saidcrucible to said pour angle, thereby to heat said lip prior to pouringof the molten metal.
 14. Automatic casting apparatus according to claiM13, wherein: said program parameters include a parameter representing asuperheat temperature in excess of said pouring temperature; saidprogrammer means produces a signal representing said superheattemperature; and said control means operates said heater in response tosaid signals to heat said metal to the molten state and then heat themolten metal to said superheat temperature while said crucible occupiessaid melt angle and to thereafter bring the temperature of the moltenmetal to said pouring temperature following heating of said cruciblepouring lip.
 15. Automatic casting apparatus according to claim 14,wherein: said control means includes means for operating said heater toheat said molten metal at a reduced heating power level during heatingof said pouring lip; and said superheat temperature, lip heat delaytime, and reduced power level are selected to effect heating of saidpouring lip to a given lip temperature and concurrent cooling of saidmolten metal approximately to said pouring temperature.
 16. Automaticcasting apparatus according to claim 10, wherein: said programparameters include a parameter representing an initial temperature ofsaid molten metal and a parameter representing a heating delay time atsaid heating power level required to heat the molten metal to a selectedtemperature less than said initial temperature; said programmer meansproduces a signal representing said initial temperature and a signalrelated to said heating delay time; and said control means includesmeans for operating said heater in response to said signals to initiallyheat said metal at said heating power level for said heating delay time,heating said metal for an additional fixed delay time, and thenalternately comparing the temperature of said molten metal to saidinitial temperature and heating said metal for said fixed delay time ata power level related to the temperature error between the metaltemperature and said initial temperature until the temperature of themolten metal approximately equals said initial temperature, all prior torotation of said crucible to said pour angle.
 17. Automatic castingapparatus according to claim 16, wherein: said crucible has a pouringlip; said program parameters include a parameter representing a lip heatangle of said crucible wherein the crucible contacts but does notoverflow said pouring lip and a parameter representing a lip heat delaytime; said programmer means produces a signal representing said lip heatangle and a signal representing said lip heat delay time; said controlmeans operates said motor in response to said signals to rotate saidcrucible to and retain the crucible at said lip heat angle for said lipheat delay time following heating of said metal to the molten state andprior to rotation of said crucible to said pour angle, thereby to heatsaid lip prior to pouring of the molten metal; said initial temperatureis a superheat temperature in excess of said pouring temperature; andsaid superheat temperature, lip heat delay time, and reduced power levelare selected to effect heating of said pouring lip to a given liptemperature and concurrent cooling of said molten metal approximately tosaid pouring temperature.
 18. Automatic casting apparatus according toclaim 17, wherein: said control means includes means for comparing thetemperature of the molten metal to said pouring temperature, andoperating said heater to bring said molten metal to said pouringtemperature after expiration of said lip heat delay.
 19. Automaticcasting apparatus according to claim 10, wherein: said programparameters include a parameter representing a rate of rotation of saidcrucible to said pouring angle; said programmer means produces a signalrelated to said rotation rate; means for sensing and generating a signalrepresenting the rotational speed of said crucible; and said controlmeans operates said motor in response to said signals to rotate saidcrucible to said pour angle at said rotation rate.
 20. Automatic castingapparatus comprising: a crucible for containing a metal to be cast; amotor for driving said crucible through a range of angular positions; aninduction heater for heating said metal to the molten state; means forsensing and generating a signal related to the angular position of saidcrucible; means for sensing and producing a signal representing thetemperature of the molten metal in said crucible; programmer meansincluding means for storing information providing a casting programrepresenting preselected program parameters including melt and pourangles of said crucible, a heating power level for said heater, and ametal pouring temperature, and selectively actuable means for readingsaid parameters in sequence in response to successive actuations of saidprogrammer means and producing a signal representing each parameter; acrucible drive controller responsive to said crucible angle signals andconnected to said motor for operating said motor to rotate said crucibleto said melt and pour angles in response to said melt and pour anglesignals; a temperature monitor connected to said thermal sensor andresponsive to said pour temperature and metal temperature signals forgenerating a controlled power level signal related to the error betweensaid pour and metal temperatures; a heat controller responsive to aidheating power level and controlled power level signals and connected tosaid heater for operating said heater at said heating power level inresponse to said heating power level signal and at a heat power levelrelated to said temperature error in response to said controlled powerlevel signal; means for applying said angle signals to said drivecontroller and said heating power level and controlled power levelsignals to said heat controller to produce a casting cycle havingsuccessive steps involving operation of said motor to drive saidcrucible to said melt angle, operation of said heater following rotationof said crucible to said melt angle to heat said metal to the moltenstate at said heating power level while said crucible occupies said meltangle and to thereafter heat the molten metal to said pouringtemperature, and operation of said motor following heating of the moltenmetal to said pouring temperature to rotate said crucible to said pourangle; and means for actuating said programmer means to advance saidprogram from one parameter to the next at the completion of eachoperation in response to a parameter signal to cause said apparatus toproceed through said casting cycle.